A Novel Multi-Criteria Local Latin Hypercube Refinement System for Commutation Angle Improvement in IPMSMs

The commutation angle, γ, of an interior permanent magnet synchronous motor's (IPMSM) vector diagram, plays an important role in compensating the back electromotive force (back-EMF); both under phase current variations and an extended speed range, is required by the application. This commutation angle is defined as the angle between the fundamental of the motor phase current and the fundamental of the back-EMF. It can be utilised to provide a compensating effect in IPMSMs. This is due to the reluctance torque component being dependent on the commutation angle of the phase current even before entering the extended speed range. A real-time maximum torque per current and voltage strategy is demonstrated to find the trajectory and optimum commutation angles, γ, where the level of accuracy depends on the application and available computational speed. A magnet volume reduction using a novel multi-criteria local Latin hypercube refinement (MLHR) sampling system is also presented to improve the optimisation process. The proposed new technique minimises the magnet mass to motor torque density whilst maintaining a similar phase current level. A mapping of γ allows the determination of the optimum angles, as shown in this paper. The 3rd generation Toyota Prius IPMSM is considered as the reference motor, where the rotor configuration is altered to allow for an individual assessment.</p

Commutation Angle Maps Evaluation for Magnet Arrangements of Interior Permanent Magnet Synchronous Machines in Electric Vehicles

© 2021 IEEE. This is the accepted manuscript version of a conference paper which has been published in final form at 10.1109/SEST50973.2021.9543397The commutation angle, γ , of an interior permanent magnet synchronous motor's (IPMSM) vector diagram, plays an important role in compensating the back electromotive force; both under load phase current variations and/or when an extended speed range, being near the constant power range, is required by the application. This commutation angle is defined as the angle between the fundamental of the phase current and the fundamental of the back-emf. It can be utilized to provide a compensating effect in IPMSMs. This is due to the reluctance torque component being dependent on the phase current before the extended speed range. A real-time maximum torque per current and voltage strategy is employed to find the trajectory and optimum commutation angles, γ , where the level of accuracy depends on the application and available computational speed. A magnet volume reduction is proposed in this paper to minimize the permanent magnet mass to motor torque density, whilst maintaining the phase current below its maximum rated value. A mapping of γ allows the determination of the optimum angles as shown in this paper. The 3rd generation Toyota Prius IPMSM is considered the reference motor, where only the rotor configuration is altered to allow for an individual assessment. The electric vehicle's performance during acceleration and deceleration using various IPMSM rotor configurations is evaluated for a given four-wheel-drive vehicle. The powertrain uses two single-gear onboard, under standard drive cycles.Peer reviewe

Simultaneous estimation of SAR, thermal diffusivity, and damping using periodic power modulation for MRgFUS quality assurance

Purpose: A crucial aspect of quality assurance in thermal therapy is periodic demonstration of the heating performance of the device. Existing methods estimate the specific absorption rate (SAR) from the temperature rise after a short power pulse, which yields a biased estimate as thermal diffusion broadens the apparent SAR pattern. To obtain an unbiased estimate, we propose a robust frequency-domain method that simultaneously identifies the SAR as well as the thermal dynamics. Methods: We propose a method consisting of periodic modulation of the FUS power while recording the response with MR thermometry (MRT). This approach enables unbiased measurements of spatial Fourier coefficients that encode the thermal response. These coefficients are substituted in a generic thermal model to simultaneously estimate the SAR, diffusivity, and damping. The method was tested using a cylindrical phantom and a 3 T clinical MR-HIFU system. Three scenarios with varying modulation strategies are chosen to challenge the method. The results are compared to the well-known power pulse technique. Results: The thermal diffusivity is estimated at 0.151 mm 2s -1 with a standard deviation of 0.01 mm 2s -1 between six experiments. The SAR estimates are consistent between all experiments and show an excellent signal-to-noise ratio (SNR) compared to the well established power pulse method. The frequency-domain method proved to be insensitive to B 0-drift and non steady-state initial temperature distributions. Conclusion: The proposed frequency-domain estimation method shows a high SNR and provided reproducible estimates of the SAR and the corresponding thermal diffusivity. The findings suggest that frequency-domain tools can be highly effective at estimating the SAR from (biased) MRT data acquired during periodic power modulation. </p

Thermal dosimetry for bladder hyperthermia treatment. An overview.

The urinary bladder is a fluid-filled organ. This makes, on the one hand, the internal surface of the bladder wall relatively easy to heat and ensures in most cases a relatively homogeneous temperature distribution; on the other hand the variable volume, organ motion, and moving fluid cause artefacts for most non-invasive thermometry methods, and require additional efforts in planning accurate thermal treatment of bladder cancer. We give an overview of the thermometry methods currently used and investigated for hyperthermia treatments of bladder cancer, and discuss their advantages and disadvantages within the context of the specific disease (muscle-invasive or non-muscle-invasive bladder cancer) and the heating technique used. The role of treatment simulation to determine the thermal dose delivered is also discussed. Generally speaking, invasive measurement methods are more accurate than non-invasive methods, but provide more limited spatial information; therefore, a combination of both is desirable, preferably supplemented by simulations. Current efforts at research and clinical centres continue to improve non-invasive thermometry methods and the reliability of treatment planning and control software. Due to the challenges in measuring temperature across the non-stationary bladder wall and surrounding tissues, more research is needed to increase our knowledge about the penetration depth and typical heating pattern of the various hyperthermia devices, in order to further improve treatments. The ability to better determine the delivered thermal dose will enable clinicians to investigate the optimal treatment parameters, and consequentially, to give better controlled, thus even more reliable and effective, thermal treatments

Three-Dimensional Magnetic Field Modeling of a Cylindrical Halbach Array

A semi-analytical description of the 3-D magnetic field distribution of a cylindrical quasi-Halbach permanent magnet array is derived. This model avoids the necessity of time-consuming finite element analyses and allows for fast parameterization to investigate the influence of the number of segments on the magnetic flux density distribution. The segmented magnet is used to approximate an ideal radial magnetized ring in a cylindrical quasi-Halbach array. The model is obtained by solving the Maxwell equations using the magnetic scalar potential and describes the magnetic fields by a Fourier series

Modeling and optimization of a tubular generator for vibration energy harvesting application

The modeling and optimization of a direct-drive contactless tubular linear generator are investigated to ensure a highly reliable device with long lifetime for vibration energy harvesting application. A slotless structure is considered to minimize force ripples and simplify the later control. A semi-analytical model based on harmonic Fourier modeling is considered for the calculation of the magnetic field generated by the permanent magnets. Electrical and thermal iterative models are coupled with the magnetic Fourier model into a general optimization tool that is fast and accurate, which is validated by means of a finite element model

Machine à double excitation à effet Vernier à commutation de flux

International audienc